[1] CNR,IST FIS COSM,I-20133 MILAN,ITALY
[2] CNR,IST TESRE,I-40126 BOLOGNA,ITALY
[3] CENS,CEA,DSM,DAPNIA,SAP,SACLAY,FRANCE
[4] UNIV PADUA,PADUA,ITALY
[5] UNIV OXFORD,OXFORD,ENGLAND
[6] UNIV LONDON QUEEN MARY & WESTFIELD COLL,LONDON E1 4NS,ENGLAND
[7] INST ASTROPHYS SPATIALE,ORSAY,FRANCE
[8] DANISH SPACE RES INST,DK-2800 LYNGBY,DENMARK
[9] ESA,ESTEC,FUTURE PROJECT STUDY OFF,NOORDWIJK,NETHERLANDS
[10] HELSINKI UNIV TECHNOL,SF-02150 ESPOO,FINLAND
[11] UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA
[12] ESA,ESTEC,DEPT SPACE SCI,NOORDWIJK,NETHERLANDS
[13] ESA,HQ,DIRECTORATE SCI PROGRAMMES,PARIS,FRANCE